1. Field of the Invention
This invention is related generally to an apparatus for controlling the position of movable handles and, more particularly, to such an apparatus used for controlling the position of implement operating handles used on hydraulically operated machinery such as large agricultural tractors and the like.
2. Description of the Prior Art
Multi-function machines often have a plurality of handles used by the operator to control the speed and direction of individual functions. An example of such a machine is an agricultural tractor used to tow and power implements. Often, these implements have one or several functions which are positioned or powered by hydraulic cylinders or by hydraulic rotary motors. An example of one such type of implement is a crop sprayer while another example is a slitter type planter for planting grain crops.
A planter machine of this type may employ several large bins for holding the seed prior to planting and a motorized auger for evenly distributing the seed to the planting heads. It may also include a motorized air compressor used to urge the seed through distribution conduits. In addition, larger planter machines of this type will often be constructed to have a central section upon which the wheels are mounted and a pair of side or wing sections used for row marking. Since such a machine is much too wide for towing on public highways when the wings are extended, it will be constructed with foldable wings. Other examples of multi-function implements include grain crop harvesting machines such as towed combines, as well as vegetable harvesting machines.
Towed implements such as the foregoing share several common characteristics. They include functions positioned by hydraulic cylinders as well as those driven by hydraulic motors, the latter often driving devices having very significant inertia. In addition, such implements need to be capable of being quickly configured for transporting, for working at their intended function or for being towed during transport or for other purposes.
These requirements place unusual demands upon the hydraulic control system of the towing tractor and, particularly, upon the ways in which the hydraulic valve control handles are positioned. The operator must be able to accurately position several handles within a short period of time while yet avoiding inadvertent movement of any of them in a way which could cause breakage of the implement or of a hydraulic component.
For example, the operator may wish to position an implement side wing to a folded position for transporting and then immediately, securely lock the wing in that position. The operator may also wish to permit a high inertia motorized function to "coast" or "float" to stop rather than stopping the function by moving the control handle quickly from an operating position to a neutral or "off" position. Rapid movement to the neutral position may cause the hydraulic valve to block the passage of oil into or out of the motor. The result may be extremely high pressure "spikes". This known problem often dictates the use of hydraulic bypass relief valves or deceleration valves to prevent physical damage to the hydraulic hoses, to the hydraulic motor or to the mechanism being driven thereby.
A float position may also be required if it is desired that the towed implement freely follow the contour of the earth rather than being in working engagement therewith. Yet another reason to use a float position is to permit an implement to rapidly descend from a raised, transport position to a working position as predetermined by mechanical stops. Moving the related hydraulic valve to the float position connects together the two operating ports of a hydraulic cylinder or the hydraulic motor so that unimpeded movement to the working position may quickly occur.
Still another demand imposed by modern implements and the tractors which tow them is that once an implement is set in an operating position, with certain functions set at operating speed, the levers controlling these functions need to be positionally retained. This frees the operator's hands for other tasks. Even with the use of detents in hydraulic valves, the forces imposed upon the valve spool at elevated operating pressures will often urge the spool out of detent to neutral. The least troublesome event which flows from this happenstance is that the operator will have to reposition the valve to the operating position and may be forced to make another pass over the affected portion of the field.
In summary, the demands of today's hydraulically powered, multi-function implements have created demands for a handle position control apparatus which will provide neutral lock out, float control, and retention of a lever in an operating position.
One approach to the control of an operating handle position is shown in U.S. Pat. No. 4,358,965. The locking mechanism described therein addresses the fact that it is often desirable to lock an operating handle in the neutral position. The mechanism does so by swinging a separately movable latching bar into a pivotable camming detent connected to the handle. No provision is made for retaining the handle in an operating position, for permitting a hydraulically powered function to "float" or for controllably decelerating a high inertia load.
Still another approach to the problem of maintaining an operating handle in a position is shown in U.S. Pat. No. 4,203,291. In the depicted apparatus, the main operating handle is depressed to disengage a pair of pins from any one of several sets of apertures which are arranged along the operating quadrant. The handle may be maintained at a position adjacent any set of apertures by engaging the pins with that set. A separate release lever is required to be operated to move the main operating handle from a neutral to an operating position. In addition to recognizing the need for a neutral lock function, this apparatus also recognizes the requirement to maintain the operating handle in any one of several operating positions, thereby freeing the operator's hands for other tasks. Notwithstanding, this control mechanism includes no feature whereby a "float" function may be obtained.
Having failed to recognize these needs, the earlier handle position control mechanisms have failed to provide a solution.
A handle position control apparatus which provides a float position, a neutral lockout function and the ability to retain the handle in an operating position would be an important advance in the art.